Multi-core network packet steering: Difference between revisions

Revision as of 13:51, 11 July 2025

Revision as of 14:10, 11 July 2025

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[[Network packet]] steering of transmittingtransmitted and receivingreceived traffic for [[Multi-core_processor|multi-core architectures]] is needed in modern network computing environment, especially in [[Data_center|data centers]], where the high bandwidth and heavy loads would easily congestion a single core's [[Queueing theory|queue]].<ref name="RSS++">{{Cite journal |last=Barbette |first=Tom |last2=Katsikas |first2=Georgios P. |last3=Maguire |first3=Gerald Q. |last4=Kostić |first4=Dejan |date=2019-12-03 |title=RSS++: load and state-aware receive side scaling |url=https://dl.acm.org/doi/10.1145/3359989.3365412 |journal=Proceedings of the 15th International Conference on Emerging Networking Experiments And Technologies |series=CoNEXT '19 |___location=New York, NY, USA |publisher=Association for Computing Machinery |doi=10.1145/3359989.3365412 |isbn=978-1-4503-6998-5}}</ref>

[[File:Simple NIC and cores architecture.png|thumb|upright=1.7|Simple graph showing the path receiving packets need to travel to reach the cores' queues]]

For this reason many techniques, both in hardware and in software, are leveraged in order to distribute the incoming load of packets across the cores of the [[Central processing unit|processor]].

On the traffic-receiving side, the most notable techniques seenpresented in this article are: RSS, aRFS, RPS and RFS.

For transmission, we will focus on XPS.<ref name="General intro">{{Citation |last=Madden |first=Michael M. |title=Challenges Using the Linux Network Stack for Real-Time Communication |date=2019-01-06 |work=AIAA Scitech 2019 Forum |url=https://arc.aiaa.org/doi/10.2514/6.2019-0503 |access-date=2025-07-10 |series=AIAA SciTech Forum |publisher=American Institute of Aeronautics and Astronautics |doi=10.2514/6.2019-0503 |pages=9-11}}</ref><ref>{{Cite web |last=Herbert |first=Tom |date=2025-02-24 |title=The alphabet soup of receive packet steering: RSS, RPS, RFS, and aRFS |url=https://medium.com/@tom_84912/the-alphabet-soup-of-receive-packet-steering-rss-rps-rfs-and-arfs-c84347156d68 |access-date=2025-07-10 |website=Medium |language=en}}</ref><br>

As shown by the figure beside, packets coming into the [[Network_interface_controller|network interface card (NIC)]] are processed and loaded to the receiving queues managed by the cores (which are usually implemented as [[Circular buffer|ring buffers]] within the [[User space and kernel space|kernel space]]).

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== Hardware techniques ==

Hardware accelerated techniques like RSS and aRFS are used to route and load balance incoming [[Network_packet|packets]] across the multiple cores' queues of a processor.<ref name="RSS++" /><br>

Those hardware supported methods achieve extremely low latencies and reduce the load on the CPU, as compared to the software based ones. However they require a specialized hardware integrated within the [[Network_interface_controller|network interface controller]] (which, for example, is usually available on more advanced cards, like the [[Data_processing_unit|SmartNIC]]).<ref name="aRFS by redhat">{{Cite web|title=aRFS by redhat|url=https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/6/html/performance_tuning_guide/network-acc-rfs|access-date=2025-07-08|website=docs.redhat.com|publisher=Red Hat Documentation|language=en-US}}</ref><ref name="aRFS by nvidea">{{Cite web|title=aRFS by nvidea|url=https://docs.nvidia.com/networking/display/mlnxofedv23070512/flow+steering#src-2396583156_safe-id-Rmxvd1N0ZWVyaW5nLUFjY2VsZXJhdGVkUmVjZWl2ZUZsb3dTdGVlcmluZyhhUkZTKQ|access-date=2025-07-08|website=docs.nvidia.com|publisher=NVIDIA Documentation Hub|language=en-US}}</ref>

=== RSS ===